Grease dispersion



Patented Jan. 1, 1952 GREASE DISPERSION George V. Browning, Schenectady,., assign'or to Standard Oil Company, Chicago, 111., a cor- 'poration-of Indiana No Drawing. Application October 26, 1949, Serial No. 123.779

2 Claims. (01. -25241.)

This invention relates to dispersion of soapoil greases and it pertains more particularly to the dispersion in a volatile solvent of an allpurpose grease composed essentially of a liquid oil retained in a mesh structure formed by interlocking fibers of a soap such as lithium soap.

An object of the invention is to provide a more simple and convenient method of dispensing a soap-oil grease than has heretofore been known. A further object is to provide an improved method and means for applying a soap-oil grease to relatively inaccessible metal surfaces, "particularly when such surfaces cannot be serviced by conventional grease guns and fittings. An important object is to provide an improved method and means for controlling the amount and uniformity of distribution of a soap-oil grease when applied to metal surfaces particularly to intricate mechanism. Other objects will be apparent as the detailed description of the 'inven tion proceeds.

The term grease'as employed in this specification refers to a heterogeneous composition in which a liquid oil, usually a refined petroleum hydrocarbon lubricating oil, is retained in a mesh structure formed by interlocking soap fibers and it does not include vegetable or mineral fats or homogeneous mixtures of 'oils with waxes, "polymers, or other components which may be added to oils for controlling their viscosity or other i physical properties. The soap structure of such a grease apparently consists of minute clusters of fibers which may be of microscopic dimensions, but which normally interlock with each other when formed in the presence of a petroleum oil and hold the oil in situ so that said oil does not separate from the grease structure on prolonged standing or with mechanical working. .Electron miscroscopic studies have shown that -the lithium soap component of a grease is in the form of fibers of the order of one micron in length, that calcium soap fibers are much longer and sodium soap fibers are still longer. However, these soap fibers may in fact be an oriented cluster or bundle of shorter fibers, the precise size and nature of which is not fully known.

I have discovered that the oil component of a soap-oil grease may be extracted from the fibrous mesh of interlaced or interlocking Isoap fibers by the use of solvents which will dissolve or reduce the viscosity of the oil component without dissolving or altering'the structural :soap com ponent. This discovery is more fully set forth .in my paper entitled A New Approach to Lubricating Grease Structure presented in October,

1949-, before the National Lubricating Grease Institute (published in The Institute Spokesman? April 1950, pages 10 to 15). If an original'soapoil grease mass of a given configuration is held quiescent during such an extraction or leaching of the liquid component therefrom, such mass will not be substantially altered in overall configuration. However, if the vessel containing the oil solution and residual soap structure is mildly agitated 'by stirring or shaking, there is an apparent break-down or disintegration of the overall structure into clusters of fibers which are dispersed throughout the solution and which will usually continue to 'be so dispersed for a period of many hours without further agitation. The striking phenomenon is that when the solvent is removed from the solution by evaporation, these clusters apparently reunite with each other and occlude or imbibe the oil to give areformed grease in substantially the same structure and physical properties as the original grease. Even if the solution containing dispersed soap fiber clusters is sprayed "on to a metal surface through an atomizer, the spraying apparently does not destroy the fiber clustres since the sprayed solution, after evaporation of solvent, leaves a thin layer of grease which is of substantially the same structure and physical properties as the original grease. 1

Inlpracticing my invention, I -leach or extract the oil component of a soap-oil grease with a volume of a volatile solvent which is at" least three or four times, and which may be as much as fifty times, the volume of the original soap oil grease. During or after. the leaching orextraction, the solution is agitated by stirring,

shaking or otherwise, to disperse minute clusters of soap fibers throughout the solution. When this dispersion is sprayed on to any surface, and the solvent permitted to evaporate from the sprayed film, the surface is coated with a soapoil grease of which the soap structure actually holds the oil in situ, the applied grease film being substantially the same in composition as the original grease. The thickness of the grease film maybe controlled by controlling the amount of volatile solvent in which the grease is dise persed and by controlling the timeand rate of spraying. The solvent is preferably anon flam mable liquid or liquefied gas of such volatility that it will readily vaporize from the sprayed film.

It is of course 'well known that soluble liquids and/or solids may be dispensed as solutions in volatile solvents and thus sprayed .on surfaces to be coated. Insecticides, oils, waxes, etc., have thus been applied to various surfaces by means of an ordinary aerosol bomb. Penetrating oils have thus been applied to springs, door hinges, etc. Heretofore, however, the lubricant thus applied was not held in place and there was always a tendency for it to run off or drain away from the surfaces. Even when the so-called dripless oils were employed on moving parts, it had to be frequently replenished because it lacked any positive structure for holding the oil in place. The outstanding feature of my invention is the dispersion of soap fiber clusters in the oil solvent solution so that the resulting sprayed film will actually be a soap-oil grease and not a simple homogeneous coating.

While the invention is applicable to soap-oil greases generally, it is most useful with lithium soap greases because of the extremely short fiber length of the lithium soap component thereof. The soap content of the grease is not critical but may vary in the relatively wide range permissible in the grease making art; for best results, how- 1 ever, the soap content should be in the range of about 4% to 20%, or approximately The lithium soap is preferably lithium stearate-although it may be lithium oleate or palmitate, or in fact anylithium soap which, when formed in the original grease, results in a fibrous structure which can be recognized with an electron microcompounded withother types of lubricant liquids or the original hydrocarbon component of a .grease may be replaced by another lubricant liquid component in the manner pointed out in the paper hereinabove referred to.

While the invention is applicable to soap-oil greases generally, it by no means follows that all grease compositions are equivalent and lithiurn soap greases appear to be in a class by themselves since they are particularly advantageous for dispersion and spray atomizing and are vastly superior to other greases for all-purpose use. However, calcium soap, sodium soap, aluminum soap, and other known soaps may be employed as the soap component of the soap-oil grease provided thatthe soap structure as revealed by an electron microscope is in the form of interlocking fibers which may be dispersed as clusters in the volatile solvent used for extracting the oil and which on vaporization of the solvent will inter- ;lock to reform the grease structure.

The solvent should be a volatile liquid or lique- 'fied gas which will dissolve the oil component of the grease without dissolving or materially altering the soap fiber cluster formation of the grease structure. For example, I may employ a volatile hydrocarbon having about 3 to 8 carbon Freon-12... (dichlorodifluoromethane) and mix- Cil 4 tures thereof, are particularly suitable per se or in combinationwith a volatile hydrocarbon solvent in such proportions as to render the latter nonfiammable. For best results, at least 4 volumes of solvent per volume of soap-oil grease and 50 volumes or more of the solvent may be employed per volume of grease where the application of extremely thin grease films is desired. On a weight basis, I prefer to employ a dispersion of grease in solvent to give a total mixture containing about 2 to 10% soap-oil grease.

To demonstrate the effectiveness of my grease dispensin method, a lithium grease containing 7.4% lithium stearate compounded with a refined petroleum lubricating oil having a viscosity 7 of 360 S. S. U. at F. was placed in an aerosol can and brought to a temperature of 50 F. At this temperature about 17 parts by weight of a 50-5O mixture of Freon-11 and Freon-12 were added per part of the lithium grease while the container was kept at approximately 50 F. The container was then closed and brought to room temperature. After about an hour, during which time the can was shaken from time to time, the dispenser was tested. Upon opening the valve, a spray was emitted which deposited a film of grease upon evaporation of the solvent. The grease had substantially the same characteristics as the original lithium grease prior to addition of the Freon.

The invention is not limited to the dispensing of lubricating greases but is also applicable to anti-rust greases wherein it is desired to hold an anti-rust composition on a surface by interlocking soap fibers. Intricate mechanism may be protected against rusting and simultaneously lubricated by thus applying mineral oil containing anti-rust. ingredients as the oil component of the grease. Similarly the grease may contain any of the known additives such as sulfur compounds for imparting extreme pressure lubricating qualities, esters for imparting high temperature stability, anti-oxidants and other additives commonly useful in oils and lubricants provided that such additives are not adversely affected by the solvent.

While the grease may be dispensed from a conventional aerosol can or bomb, it is desirable in some instancesv that the can or bomb be provided with a tip orconduit'extending beyond the edge of the dispensing vessel so that the introduction of the grease spray to small openings may be facilitated. An outstanding feature of the invention is the use of a volatile solvent such as Freon for three. distinct purposes: (1) extracting the oil from a pre-formed lithium soap structure, (2) dispersing minute clusters of soap fibers without dissolving them or substantially altering their orientation, and (3) propelling the dispersion onto the surface to be coated by their self developedpressure at normal temperatures. The invention'may be employed generally where it is present practice to apply oil dropwise to metal surfaces, the grease spray having the important advantage of enabling the deposition of a uniform coat over all desired surface area, controlling the thickness of the coat (by varying the amount of solvent employed with a given amount of grease as wellas varying the time and rate of spraying), and most important of all, holding the oil in situ on the sprayed surface by the reformation of the cellular lattice of interlacing soap fibers so that there is no tendency of the oil to run off the surface or leak out of the grease film.

I claim:.

1. An aerosol dispensable lubricant composition which consists essentially of a lithium soapoil grease having a soap content in the range of about 4 to 20 per cent by weight and characterized by a soap fiber length of the order of one micron dispersed in a mixture of trichloromonofiuoromethane and dichlorodifluoromethane, the amount by Weight of the lithium soapoil grease in the total composition being in the range of .5 to 20 per cent and said composition being further characterized by having the oil component of the grease dissolved in the mixture of trichloromonofiuoromethane and dichlorodifluoromethane at a temperature and pressure to maintain these components in liquid phase without dissolving the lithium soap fibers whereby unaltered lithium soap fiber clusters are retained as a suspension therein so that when said suspension is sprayed on a surface to be coated, the trichloromonofiuoromethane and dichlorodifluoromethane will evaporate and the deposited film will consist essentially of a grease consisting of meshed lithium soap fibers with oil retained therein, said grease having substantially the same structure and physical properties as the original lithium soap grease.

2. An aerosol dispensable lubricant composition which consists essentially of a lithium soapoil grease having having a soap content in the range of 4 to 20 per cent by weight and char- 6 acterized by a soap fiber length of the order of one micron dispersed in a mixture of trichloromonofluoromethane and dichlorodifiuoromethane, the amount by Weight of lithium soap-oil grease in the total composition being in the range of .5 to 20 per cent, in which composition all components are in the liquid phase except the soap fibers and the soap fibers are undissolved and in the solid phase, such composition having been prepared by placing said lithium soap-oil grease in a container, cooling to a temperature of about F., adding the trichloromonofiuoromethane and dichlorodifluoromethane at said temperature, closing said container, raising the temperature to about room temperature and agitating the mixture in the container to effect said dispersion.

GEORGE V. BROWNING.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,892,750 Rotheim Jan. 3, 1933 1,995,371 Werder Mar. 26, 1935 2,128,433 Rotheim Aug. 30, 1938 2,449,114 Gebauer Sept. 14, 1948 

1. AN AEROSOL DISPENSABLE LUBRICANT COMPOSITION WHICH CONSISTS ESSENTIALLY OF A LITHIUM SOAPOIL GREASE HAVING A SOAP CONTENT IN THE RANGE OF ABOUT 4 TO 20 PER CENT BY WEIGHT AND CHARACTERIZED BY A SOAP FIBER LENGTH OF THE ORDER OF ONE MICRON DISPERSED IN A MIXTURE OF TRICHLOROMONOFLUOROMETHANE AND DICHLORODIFLUOROMETHANE, THE AMOUNT BY WEIGHT OF THE LITHIUM SOAPOIL GREASE IN THE TOTAL COMPOSITION BEING IN THE RANGE OF .5 TO 20 PER CENT AND SAID COMPOSITION BEING FURTHER CHARACTERIZED BY HAVING THE OIL, COMPONENT OF THE GREASE DISSOLVED IN THE MIXTURE OF TRICHLOROMONOFLUOROMETHANE AND DICHLORODIFLUOROMETHANE AT A TEMPERATURE AND PRESSURE TO MAINTAIN THESE COMPONENTS IN LIQUID PHASE WITHOUT DISSOLVING THE LITHIUM SOAP FIBERS WHEREBY UNALTERED LITHIUM SOAP FIBER CLUSTERS ARE RETAINED AS A SUSPENSION THEREIN SO THAT WHEN SAID SUSPENSION IS SPRAYED ON A SURFACE TO BE COATED, THE TRICHLOROMONOFLUOROMETHANE AND DICHLORODIFLUOROMETHANE WILL EVAPORATE AND THE DEPOSITED FILM WILL CONSIST ESSENTIALLY OF A GREASE CONSISTING OF MESHED LITHIUM SOAP FIBERS WITH OIL RETAINED THEREIN, SAID GREASE HAVING SUBSTANTIALLY THE SAME STRUCTURE AND PHYSICAL PROPERTIES AS THE ORIGINAL LITHIUM SOAP GREASE. 